Skid plate for concrete saw

ABSTRACT

A skid plate for a concrete saw is integrally cast having two end mounting portions and a middle portion with a slot in the middle portion. A horizontal slot in a leading end mounting portion cooperates and a vertical slot in the trailing end portion releasably engage pins on the saw to allow the skid plate to be easily fastened to and removed from the saw. A spring loaded latch mechanism holds the pins in the slots.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) ofprovisional applications Ser. No. 60/576,476, filed Jun. 3, 2004, thecomplete contents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Slotted skid plates are used with concrete saws to cut concrete beforeit is hardened to the green stage. This is described in U.S. Pat. No.4,769,201. But the concrete is very abrasive. Thus, the skid plates aremade of steel to resist the wear from sliding over the concrete surfaceand to resist the wear from the abrasive concrete carried by the bladeat the cutting edge and which widens the slot in the skid plate. Theskid plates were made of sheet steel and bent to the desired shape. Butthe steel skid plates warp during manufacture and use and that causesraveling as the cut concrete grooves ravel unless the skid plates areflat against the concrete during cutting. There is thus a need for animproved skid plate that remains flat against the concrete aftermanufacture and during use.

One patent addresses this problem of the non-flat skid plates by using atruss to warp the skid plate into a desired configuration, as describedin U.S. Pat. No. 5,507,273. But adjusting the truss and fixing the trussto lock in the desire distortion is complex and time consuming. Indeed,it is so difficult that special equipment and methods are used, asdescribed in U.S. Pat. No. 5,689,072. There is thus a need for a betterway to achieve a flat skid plate during cutting. A less expensive way tomake skid plates is also desirable.

The skid plates are fastened to the saw by inserting pins through holesin the distal ends of spring loaded pistons The pistons resiliently urgethe skid plate against the concrete surface during cutting. Because thealignment of the skid plate with the saw blade affects the quality ofthe groove cut in the concrete, the pins holding the skid plate to thesaw have a very tight fit with the mating holes in the pistons. Butremoving the pins is difficult because the pins often freeze in place.The skid plates thus become difficult to remove and that encouragesworkers to leave them as long as possible, and often too long.Unfortunately, the skid plates wear, sometimes after as little as 1200feet of cutting and the quality of the cut groove deteriorates with thewear. There is thus a need for a better way to fasten the skid plate tothe saw and to make it easy to remove a used skid plate from the saw andto fasten a replacement skid plate to the saw.

BRIEF SUMMARY OF THE INVENTION

A cast skid plate for a concrete cutting saw is provided. The saw has arotating blade with sides and rotating about a rotational axis to cut agroove in a concrete surface during use of the saw. The skid plate hasan elongated support portion having a longitudinal slot therein sized tofit within about ⅛ inch or less of the sides of the concrete cuttingblade during use of the skid plate. The elongated support is slightlybowed an amount selected to substantially counteract bowing of the skidplate that occurs when the elongated support is urged against theconcrete surface during cutting of the concrete. The bow is cast intothe skid plate. At least one saw mounting portion is provided, and isoffset from the elongated support. The elongated support and at leastone saw mounting portion are also integrally cast with the skid plate.

Further variations of the cast skid plate cause the curvature of abottom surface of the skid plate to extend beyond leading and trailingend portions of the skid plate by about ⅛ inch or less. The skid platebows toward the concrete. Preferably there are two mounting portionsforming a front and rear mounting portion, one each at an opposing endof the elongated support portion. Advantageously, but optionally, thereis a front mounting portion having a front mounting yoke, and there is arear mounting portion having a rear yoke. The elongated portion and atleast one mounting portion are preferably cast of metal other than iron,preferably aluminum, but could be cast of a polymer or of a ferrousalloy.

In a further variation the cast skid plate has two mounting portions,one of which comprises a slot extending along an axis toward and awayfrom the elongated support portion and configured to receive a pinorientated generally parallel to the rotational axis. The other mountingportion comprises a slot that is generally parallel to the concretesurface during cutting. Preferably, but optionally, a snap lock orspring loaded clip holds a mating portion of the saw engaged in thevertical slot in order to provide for a quick-release connection withthe skid plate.

In a further variation the skid plate has a leading and trailing end andthe leading end of the skid plate has an end that is angled relative tothe longitudinal slot. Moreover, the leading end of the skid platepreferably has a V shaped configuration in the plane of the elongatedportion with the point of the V oriented away from a trailing end andtoward the leading end and that helps shove concrete debris from cuttingout of the way of the skid plate so the debris is not run over by theskid plate.

The skid plate preferably comprises a single part connected to the sawat opposing ends. But in a further embodiment the skid plate is formedby two separate segments each of which has a separate saw mount portion,and each of which has a slot therein which slot extends along a portionof the cutting blade during use of the saw.

There is also advantageously provided a skid plate having two sawmounting portions on the skid plate and an elongated support portionwhich are integrally cast of metal. The saw mounting portions are offsetfrom the support portion a predetermined distance. An elongated slot iseither cut into the support portion or integrally cast with the supportportion. The slot is sized relative to the cutting blade to support theconcrete surface during cutting so cutting does not produce unacceptableraveling of the cut groove during use of the skid plate. The skid plateis preferably cast of non-ferrous metal, but an iron based metal couldbe used as could polymers. The leading end of the skid plate preferably,but optionally also has an angled end forming a V with the apex of the Vfacing forward and in the same plane as the slot. The support portion isalso preferably, but optionally curved about an axis generally parallelto the first axis by an amount selected to at least partially offset thedeformation of the skid plate occurring when the saw urges the skidplate against the concrete surface during cutting.

There is also provided a further skid plate having first means formounting the skid plate to the concrete saw and second means forsupporting the concrete surface during cutting. The first and secondmeans are simultaneously and integrally cast. The first and second meansare preferably formed of cast metal, and more preferably cast of a metalthe dominant portion of which is other than iron. The first and secondmeans could be cast of a polymer. The second means preferably, butoptionally comprises a slot that is cut in the elongated portion afterthe elongated support skid plate and mounting portion are cast, but thesecond means could comprise a slot that is cast in the elongatedportion. As with the prior embodiments, there is preferably an angledfront end on the support portion.

A further embodiment uses a replaceable plate that removably fastens tothe skid plate and abuts the bottom of the skid plate. Various fasteningmechanisms can be used, including snap locks that cooperate with thesides or flanges on the skid plate, threaded fasteners that engage theskid plate at various locations, resilient prongs that engage the edgesaround holes or slots in the skid plate, and adhesives. The mechanismsfor fastening the plate to the skid plate restrain the plate and skidplate from longitudinal movement, and lateral movement, so that a slotin the plate aligns with the blade extending through the slot in theskid plate, in order to prevent raveling of the concrete surface duringcutting. The slot can be formed in the plate, or cut by the blade. Theslot can end internally to the plate, or can extend to a trailing edgeof the plate. A partial slot or widened slot can be used at the trailingend of the plate in order to avoid having the plate trowel over the cutgroove.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a saw with a cast skid plate;

FIG. 2 is a top perspective view of the cast skid plate of FIG. 1;

FIG. 3 is a perspective view of the cast skid plate of FIG. 2 from theother end of the skid plate;

FIG. 4 is a perspective view of the bottom of the skid plate of FIG. 1;

FIG. 5 is a perspective view of a further embodiment of a skid platewith a side mounting portion;

FIG. 6 is a side view of the skid plate of FIG. 2;

FIG. 7 is a sectional view taken along section 7-7 of FIG. 6;

FIG. 8 is an exploded perspective view of a saw blade mounting block andthe skid plate of FIG. 1;

FIG. 9 is a perspective view of the clip of FIG. 2;

FIG. 10 is a partial side view of a rear mount taken from FIG. 2;

FIG. 11 is a perspective view of a further embodiment of the skid plateof FIG. 1;

FIG. 12 is a side view of a further embodiment of a one or two-part skidplate;

FIG. 13 is an exploded perspective view of a further embodiment showinga front segment of a skid plate;

FIG. 14 is a perspective view of the skid plate of FIG. 13 with aportion cut-away to show the connection to a mounting shaft or piston ofa saw;

FIG. 15 is a partial view of a front mount with a motion limit stop;

FIG. 16 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a releasable fastener;

FIG. 17 is a perspective view of the skid plate of FIG. 16;

FIG. 18 is a further embodiment of the skid plate of FIG. 16;

FIG. 19 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a further releasablefastener;

FIG. 20 is a perspective view of the further releasable fastener of FIG.19;

FIG. 21 is a perspective view of the skid plate of FIG. 19;

FIG. 22 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a releasable fastener;

FIG. 23 is a perspective view of the skid plate of FIG. 22;

FIG. 24 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a releasable fastener;

FIG. 25 is a perspective view of the skid plate of FIG. 24;

FIG. 26 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a releasable fastener;

FIG. 27 is a perspective view of the skid plate of FIG. 26;

FIG. 28 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a releasable fastener;

FIG. 29 is a perspective view of the skid plate of FIG. 28;

FIG. 30 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a releasable fastener;

FIG. 31 is a perspective view of the skid plate of FIG. 30;

FIG. 32 is an exploded perspective view of a further embodiment of acast skid plate showing a removable plate held by a releasable fastener;and

FIG. 33 is a perspective view of the skid plate of FIG. 32.

DETAILED DESCRIPTION

Referring to FIGS. 1-8, a cast skid plate 10 is shown having a leadingor front end 12, a rear or trailing end 14 and a middle portion orsupport portion 16. The skid plate is preferably cast of metal, butpolymers could be used, especially if cast with metal inserts asdescribed later. A slot 18 extends through the middle portion 16 socutting blade 20 rotating about drive axis 21 can cut the concretesurface 22 on which the skid plate 10 moves during cutting. A lowersurface 24 (FIG. 4) of the skid plate 10 abuts the concrete duringcutting and forms an elongated support portion which supports theconcrete surface 22 along the cutting blade 20 during cutting. In thedepicted configuration the lower surface 24 extends across all of themiddle portion 16 and parts of the front 12 and rear 14 portions of theskid plate.

During use, a wheeled saw (FIG. 1) rotates the cutting blade 20,preferably but optionally, in an up-cutting direction to cut grooves 25in the concrete surface 22. Front and rear, spring loaded mounts 32, 36,(FIG. 8) resiliently urge the skid plate 10 against the concrete surface22 during cutting. A groove, slot or tunnel 23 (FIG. 4) is formed in thelower surface 24 at the trailing end of the slot 18 in order to avoidtroweling over and possibly closing the groove cut by the blade 20 thatextends through the groove 18 to cut groove 25 in the concrete.

As used herein the term front or forward or leading refers to thedirection in which the saw normally moves when doing the majority ofcutting on the concrete surface 22. The concrete saw could be pulledbackwards and it would cut a groove in the concrete, but the saw is notdesigned to go that way for any substantial distance. The term rear ortrailing refers to the direction opposite front or forward or leading.The term up or upward or above refers to a direction away from theconcrete during cutting. The term down or downward or below refers to adirection toward the concrete surface during cutting.

Referring to FIGS. 2 and 8, front mounting yokes 30 are on the top ofthe front end 12 and releasably connect to the front mount 32 on thesaw. The front mount is shown as spring loaded pistons 32 but need notbe so. Rear mounting yokes 34 are on the rear 14 and releasably connectto the rear mount 36 on the saw. The mounting yokes 30, 34 areintegrally cast with the front and rear ends 12, 14, respectively, andform front and rear mounting portions. Various configurations can beused for the mounting portions 30, 34. The mounting portions 30, 34 areoffset relative to the bottom surface 24 of the skid plate 10.

In the depicted embodiment, the front mounting portion 30 comprise apair of spaced-apart mounts 30L, 30R, with one mount on each side of thelongitudinal axis 64. Each front yoke mount 30 has a slot 38 openingrearward with a slightly downwardly inclined lower side 40 on the wallforming the slot. The opposing, upper side of each slot 38 is generallyhorizontal. The downwardly inclined side 40 forms a wider opening to theslot 38 which makes it easier to insert a mating front projection 42(FIG. 8) extending from the front piston 32 on the saw. Preferably, butoptionally, the projection 42 comprises a steel pin or roller passedthrough a distal end of the front piston 32, with the distal end of thepiston fitting between the front yokes 30. The use of horizontal slotsin front yokes of a skid plate, located to engage a front pin throughthe front piston 32 are found on prior art saws.

The rear mounting yoke 34 also preferably has two spaced apart mounts34L, 34R, each located on opposing sides of the longitudinal axis 64.Each rear mount 34 has a rear slot 44 opening upward to receive a rearprojection 46 fastened to the rear piston 36 on the saw. In thisembodiment the rear yokes 34 are located on opposing sides of thelongitudinal axis 64, and each individual yoke further has a slot 44opening upward with the slot 44 preferably being wider at the top thanthe bottom which makes it easier to insert the mating projection 46(FIG. 8) extending from the rear piston 36 on the saw. Preferably, butoptionally, the projection 46 comprises a steel pin or roller passedthrough a hole in the distal end of the rear piston 36, with the distalend of the piston fitting between the rear yokes 34.

The front pin 42 on front piston 32 is slid horizontally into the slot38 on the front yoke 30. The spacing between the front and rear pins 42,46 is such that when the front pin 42 is near to or abuts the end of thefront slot 38 then the rear pin 46 aligns with the rear slot 44 so therear piston 36 is then slid between rear yokes 34 with the rear pin 46engaging the bottom of slot 44 in rear yoke 34. The relative movementcan be achieved by moving the skid plate and its rear slot 44 toward therear pin 46 or moving the saw and rear pin toward the skid plate.Preferably, the front pin 42 does not abut the end of the front slot,but is near the middle of the front slot 38.

Referring to FIGS. 2 and 8-10, clip 48 (FIG. 2) on the rear portion 14or other fastening mechanism holds the rear pin 46 in the slot 44 andprevents unintentional disengagement of the rear pin 46 from the rearslot 44. The clip 48 is preferably, but optionally a spring steel stripof shaped metal fastened to the rear end 14 of the skid plate 10. Afastener passing through the clip 48 and into a hole in a land formed inthe rear 14 can hold the clip, with such a hole and land shown in FIG.3. The clip 48 has a flat base 50 which joins a curved portion thedistal part of which forms a locking portion as it abuts the rearprojection 46. The distal end 54 of the clip forms a tang or handle toengage a user's finger to move the clip locking portion 54 to disengagethe clip and allow the rear projection 46 to be removed from the rearslot 44. Further, during insertion the rear pin 46 abuts the tang 54 ata downwardly inclined angle to move the tang 54 laterally out-of the wayso the pin 46 can readily enter the slot 44 without manually touchingthe clip 48. After the pin 46 passes the juncture of the tang 54 and theengaging portion 52, then the clip 48 resiliently urges the pin 46toward the bottom of the slot 44. The clip 48 can be rotated 180° andfunction the same way.

Preferably a user need not manually engage the tang 54 to release therear pin 46 from the rear yoke 34. A rear tab 56 extends rearward fromrear 14. The rear tab 56 preferably, but optionally has an alignmentindicator 58, such as a point, notch, hole or slot located in the sameplane as the slot 18 and blade 20 so a user can align the alignment 58with the groove 25 to help guide the saw during cutting. Such alignmentindicators are known in the art. But the rear tab 56 is preferably largeenough that a user can step on it and lift up on the saw, causing therear pin 46 to overcome the retention force exerted by spring clip 48 inorder to disengage the rear pin 46 from the yoke 34. The clip 48 thusprovides releasable means for retaining the rear pin 46 in the rear slot44 of rear yoke 34. Other releasable snap locks are known and can beused here, including over-centered locks. Other releasable lockingmechanisms can also be used, including slidable locks.

The rear yoke 34 has a front projection 34 a and a rear projection 34b(FIG. 10) with the space between them forming slot 44. The bottom of theslot is curved to accommodate rear pin 46 and is preferablysemi-circular in shape of a radius slightly larger than that of the rearpin 46. The side of projection 34 b forming the slot 44 is straight andpreferably vertical. The opposing side of the slot 44 formed byprojection 34 a is inclined forward at an angle θ of about 2-10° fromthe vertical beginning at about the radius of the curved bottom of theslot 44, or slightly above that radius. The inclined side of slot 34 aprovides a wider opening to the slot 44 and makes it easier to insertthe rear pin 46 into the slot.

By inclining the side of the slot 44 formed by projection 34 a forward,the pin 46 urges the skid plate 10 forward relative to the pin 44 andthe saw, with the front pin 42 being held in a generally horizontal slot38 to float in that front slot 38. Thus, the position of the skid plate10 is determined by the sides of the rear slot 44 engaging the rear pin36 while the front end of the skid plate floats in the horizontal slot38. There is always some risk the front pin 42 can hit the end of thefront slot 38 before the rear pin 46 is positioned in the bottom of slot44, and if only a slight interference is caused it will be accommodatedby movement of the pistons 32, 36 and pins 42, 46, but it will result ina snug engagement of the front pin 42 with the front end of front slot38. That will result in little misalignment of the skid plate 10relative to the mounting portions 32, 36 of the saw.

If it were reversed so that the side of the slot 44 formed by the rearprojection 34b was inclined rearward to form a wider opening of the slot44 (FIG. 6), then when the rear pin 46 hit the yoke 34 and moves towardthe bottom of slot 44 the pin 46 will push the skid plate 10 rearwardbut the front end of the skid plate would still float or be accommodatedby the permissible movement allowed from horizontal slot 38. But therewould be slightly more permissible movement between the front pin 42 andthe front slot 38 and thus slightly more possible misalignment of theskid plate 10 relative to the mounting portions 32, 36 and relative tothe saw. The clip 48 provides a spring force to resiliently urge therear pin 46 into the rear slot 44 and if the front slot 38 is not longenough, the front pin 42 is also resiliently urged against the front endof front slot 38.

The upward opening slot 44 in the rear yokes 34 cooperates with the clip48 to provide a means for releasably fastening the rear of the skidplate 10 to the saw. This releasable connection is believed to be easierto achieve than the prior art which inserted a pin horizontally throughaligned holes in one or two yokes to mate with a close-tolerance holethrough the rear piston 36. The rear pin 46 snaps into the slot 44 andis resiliently held there by the resilient clip(s) 48. The connection isalso believed to be easier to release than the prior art connections asthe pin 46 is not believed to adhere to the slot 44 and rear yoke 34during use. Further, the finger or foot activated disengagement of theclip(s) 48 is believed to be considerably easier than the prior artdisconnection of a curved spring from opposing ends of the fasteningpin. Moreover, because the rear yoke 34 and slot 44 are cast along withthe skid plate 10, the location and alignment of the skid plate relativeto the mounting slot 44 are believed to be cheaper to make while moreaccurate. The prior art required not only making a rear yoke accurately,but required aligning it to a flexible platform on a strip of metal andthen fastening it to the strip of metal without shifting position. Theone-piece cast skid plate 10 provides more consistently locatedsurfaces, and the casting can be more accurately machined, ground or cutto further increase the accurate location of the mounting surfaces(e.g., slots 38, 44) relative to other features of the cast skid plate10.

Referring to FIGS. 1, 3, 4 and 6, the leading end 12 of the cast skidplate 10 is preferably, but optionally, angled relative to the directionof travel along groove 25 rather than perpendicular to the groove and tothe direction of travel as in the prior art: This angled leading end ofthe skid plate which is in contact with the concrete surface is referredto as angled leading end 60. Preferably, but optionally, two angled ends60, 62 are used to form a V-shape on the bottom surface 24 of front end12 of the skid plate 10, with the apex of the V shaped end located toalign with the groove 25 cut in the concrete. Thus, the intersection ofangled ends 60, 62 is preferably in the plane containing cutting blade20. That location also usually corresponds with the center of the skidplate 10 along which the longitudinal axis 64 of the skid plate 10extends.

The angled front end helps the skid plate to avoid running over concretethat is removed during cutting. The blade 20 preferably rotates in anup-cut direction and if the concrete debris removed to form the cutgroove 25 get in front of the skid plate then the skid plate 10 can rideover the debris. That can not only push the concrete debris into theconcrete surface 22 and damage the finish on the surface, but the debriscan tilt the skid plate causing the blade 20 to cut and weaken or widenthe slot 18 in the skid plate, or it can tilt the saw and rotating blade20 causing raveling of the cut groove 25. The inclined angle of ends 60and/or 62 on the front end 12 urges any concrete debris to one side ofthe skid plate. A single inclined end 60 could be used, with the inclinebeing constant (i.e., straight) or variable (i.e., curved). But a singleinclined end could have to move concrete debris across the entire widthof the skid plate, whereas two inclined ends 60, 60 forming a V-shapedend centered on the middle of the skid plate, need only move debrisalong half the width of the skid plate 10. Thus, two inclined ends 60,62 are preferred. The angle of inclination will vary, but isadvantageously about 100° or more measured on either side of thelongitudinal axis 64 of the skid plate, and preferably about 110-40°.

The front end 12 is also preferably, but optionally inclined relative tothe concrete surface 22 so that a portion of the front end 12 extends infront of and over the angled end(s) 60, 62, to form one, and preferablytwo inclined surfaces 66, 68. The inclined surfaces 66, 68 are inclinedfrom the leading end of the front end 12 toward the bottom surface 24 ofthe skid plate 10. While it might appear that inclined surfaces 66, 68would make it easier for the skid plate 10 to ride over concrete debris,it is believed that inclining the surfaces 66, 68 toward-the concretesurface 22 and toward the bottom 24 will cause the larger concretedebris to roll aside easier or to break up easier and move aside easier.

The front ends 60, 62 and inclined surfaces 66, 68 are integrally castwith the skid plate 10. As desired, further grinding or machining orcutting of the cast skid plate can more accurately define these ends 60,62 and inclined surfaces 66, 68. Likewise, the tunnel, groove or slot 23is also integrally cast with the skid plate 10, but could be furtherdefined by grinding, cutting or machining if desired.

The front and rear ends 12, 14 are advantageously solid in order toprovide increased stiffness. But they could be made of a rib-stiffenedstructure which would still be suitable for even metal casting. A highstiffness is desired in order to avoid undesirable flexing and to helpmaintain the bottom 24 of skid plate 10 in contact with and supportingthe concrete surface 22 during cutting. Support is especially importantat the location where the up-cutting edge of the blade 20 leaves theconcrete surface 22. Insufficient support causes raveling of the cutgroove, as shown by undesirable spalling and roughness adjacent the cut.The skid plate 10 can be cast with a pre-selected flexibility and thusavoid the cost, complexity and variability in the prior art strip-metalskid plates.

Advantageously the cast skid plate 10 is cast with a slight bow in adirection selected to offset the bowing caused when the weight of thesaw is placed on one or both of the mounting yokes 30, 34. When theweight of the saw presses the skid plate 10 against the concrete surface22, then the skid plate bottom 24 is flat against the concrete surface.This cast-in curvature generally causes the bottom portion 24 to bowconvexly usually about an axis parallel to rotational axis 21, but itcould vary with the mounting configuration of the saw, and could causethe bottom portion 24 to be concave. The curvature usually results inthe middle of the skid middle portion 18 being less than about 0.25inches (about 63 mm) from the distal ends 12, 14, and more often lessthan about ⅛ of an inch less. Depending on the particular design of theskid plate the stiffness can vary and thus the amount of curvature thatis cast into the bottom 24 will vary. Longer skid plates 10 accommodatelarger cutting blades 20, and the amount of desired flexibility canvary. But for a given weight of saw and a given configuration of skidplate 10, the deformation of the skid plate 10 can be predetermined, andthe appropriate curve can be cast in the bottom surface 24 of skid plate10. Die cast aluminum is believed suitable for achieving tolerances of0.002-0.003 inches. If further accuracy is desired beyond the tolerancesand accuracy achieved by the casting method employed, then the bottomsurface can be further machined, cut or ground to achieve a desiredaccuracy. If a softer metal is used like aluminum, the surface ispreferably anodized or otherwise hardened or coated with a hardermaterial to better resist abrasion from the concrete surface 22 duringcutting.

Referring to FIGS. 2-3 and 6-7, the stiffness of the skid plate 10 canbe varied as desired either along the longitudinal axis 64, or laterallyor perpendicular to that axis in a plane parallel to the bottom 24. Theparticular configuration will vary with the material used to cast theskid plate and the size of blade 20 and the weight of the saw. The ends12, 14 are relatively rigid to avoid localized deformation where theyokes 30, 34 transfer the weight of the saw to the skid plate 10. Acentral stiffening rib 70 runs along the longitudinal axis 64 of theskid plate 10 with the blade slot 18 being cut or formed in this rib.The front end 12 preferably, but optionally has a boss 66 (FIG. 2)extending toward the trailing end and preferably ending before theleading end of the slot 18. The boss 66 stiffens and stabilizes the skidplate 10 adjacent the leading end of the slot 18 where the up-cuttingblade exits the concrete. The boss 66 is preferably, but optionally,angled so concrete debris removed by the blade 20 are urged towardeither side of the skid plate 10.

Opposing side ribs 72, 74 extend along each opposing side of the skidplate parallel to the central rib 72 and the longitudinal axis 64. Theribs 72, 74 have a constant height along their length, exceptimmediately adjacent the front end 12 as discussed later. The side ribs72, 74 preferably, but optionally, help reduce torsion and bending,especially when coupled to the stiff ends 12, 14. A shallow concavegroove which is aligned with the longitudinal axis 64 extends on eitherside of the center rib 70, between the center rib 70 and each adjacentside rib 72 and 74. The concave groove reduces material used to cast theskid plate 10, and thus reduces cost while providing the desiredstiffness. The concave grooves also collect concrete debris removed bythe blade 20 when the cut groove 25 is formed.

The side ribs 72, 74 preferably extend continuously from the front end12 to the rear end 14 and join those ends. At the front end 12, the sideribs 72, 74 preferably, but optionally increase in height to form a pairof side shields 76, on each side. The side shields help prevent concretedebris from falling off the skid plate at the front where there is agreater possibility of being run over by the skid plate.

The trailing end 14 could have these side shields 76, but advantageouslydoes not have them as it is desirable for the concrete debris to falloff the trailing end of the skid plate. Thus, it is advantageous to havethe side ribs 72, 74 slightly lower toward the trailing end 14. Further,one or more recesses 78 are preferably, but optionally formed in therear 14 of the skid plate to accumulate concrete debris.

The concrete saw encloses the cutting blade 20 in a blade housing 76(FIG. 1) and often also has a splash shield at the end of the cuttingblade 20 where the saw blade exits the concrete and sometimes also atthe end of the cutting blade where the blade enters the concrete. Thesplash shield(s) help prevent concrete debris from being thrown by thecutting blade. When an up-cutting rotation is used on blade 20 thesplash shield prevents concrete from being thrown in front of the skidplate where it could be run over by the skid plate. The front 12 andrear 14 of the skid plate 10 are configured to accommodate the splashshields. The splash shields are typically located within an inch or lessof the ends of the cutting blade 20, and the front end 12 must thus endbefore it hits the splash shield. The same applies to the rear end 14 ifa rear splash shield is used. Further, the splash shield may move towardand away from the concrete as the resiliently mounted pistons 32, 36allow the cutting blade to move relative to the concrete surface 22.Thus, the height of the middle portion 16 of the skid plate and theheight of the ends 12, 14 must accommodate the potential motion of theshield.

The skid plate 10 is preferably cast of metal, such as zinc, aluminum orother alloys. A cast aluminum alloy, 380 series, with a hard anodizedcoating is believed preferable. Die casting is believed suitable, butsand casting, metal injection, investment casting, powdered metal,centrifugal casting or rotary casting are also believed usable and allare referred to herein as “casting.” A forged metal skid plate is alsobelieved suitable, and the skid plate can be machined out of a block ofmaterial, preferably metal. The specific casting method used will varywith the tolerances desired and will likely change with improvements incasting technology. These casting metals are softer than the strip steelpreviously used, and thus the skid plates 10 are usually much thicker inorder to provide the desired stiffness and wear resistance. A thicknessof about ¼ to ⅜ inches at the center rib 70 is believed suitable whenthe skid plate 10 is made of aluminum. The thickness used will vary withthe materials used and with the wear life that is sought to be achieved.

It is believed to be possible to mill the skid plate 10 out of a billetof steel and then optionally heat treat the steel or harden the bottomsurface 24 to achieve a hardened, steel skid plate having the featuresdescribed herein. This is not as desirable because of the difficulty andcost in machining the steel. The same machining could be done with abillet of metal other than steel, such as aluminum, with a hardeningformed on the bottom surface 24.

The skid plate 10 could be cast of iron based alloys. The iron basedalloys are less desirable as they melt at higher temperatures, areheavier, and arc more difficult and expensive to cast. But preferablythe skid plate 10 is cast of a metal the dominant portion of which isother than iron.

It is also believed that polymers could be used to cast the skid plate10, especially high density polymers such as high density polyurethane,glass filled plastics or carbon fibers. Polyacrylate is also believedsuitable. Polymers are not believed to be as desirable as metal becauseof potential excessive wear at the up-cutting edge of the blade, andbecause the harder concrete debris can embed in the softer polymers andthus be dragged along the concrete surface by the skid plate to scratchthe surface.

Polymer skid plates with metal inserts at the location of the up-cuttingedge of the blade 20 are believed suitable. The inserts preferablyextend to the surface abutting the concrete and may extend to an uppersurface of the polymer, or may be embedded in the polymer. Further, apolymer could be cast over a thin steel skid plate to add furtherthickness and support and to further define the shape of the skid plate10. The harder metal skid plate would be located to abut the concrete.The metal skid plate preferably has tangs or protrusions embedded in theskid plate so the metal is not removable, but the metal could beremovably fastened to the skid plate. Removable connections are shown inU.S. Pat. No. 6,736,126, the complete contents of which are incorporatedherein by reference. In that patent a polymer sheet is an overlay on ametal skid plate and the polymer abuts the concrete. While thatconfiguration is usable with the present embodiments, preferably a metalsheet overlays a polymer base which is connected to the saw, with thepolymer base connected to the metal skid plate using the embodiments ofthat patent.

Referring to FIG. 11, a further embodiment is shown. In this embodimentthe front yoke 30 is as previously described but the rear yoke 34 lacksthe slot 40 (FIG. 2) and instead has a generally horizontal hole 86through each of the yokes 34, with the hole sized to receive a pin 88which extends through mating holes in the rear piston 36. This is thetraditional pinned connection used in the prior art, and has thedisadvantage of difficulties in removing and reinserting the pin 88. AC-clip spring (not shown) fastens to opposing ends of the pin to preventit from falling out of the piston.

The rear end 14 has a boss 90 extending forward and ending shortlybefore the trailing end of slot 18. This provides localized stiffness atthe center of the skid plate, and that is especially useful if thecutting blade 20 exits at the trailing end of the slot 18, but the boss90 could be used even if that were not the cast. The boss is angled andinclined so that it urges concrete debris on the skid plate towardeither side of the skid plate.

In this embodiment, the side ribs 72, 74 are not of uniform height asthe front and rear ends of the ribs are higher and taper to a lower ribheight at about the middle of the length of the skid plate 10. Thisprovides more torsional movement of the skid plate and allows bendingtoward the middle of the skid plate. The trailing end of the side ribs72, 74 preferably, but optionally have openings 92 formed in them inorder to allow concrete debris to more easily fall of the skid plate 10.The central rib 70 is less pronounced in this embodiment and thus not ashigh or thick as in the first embodiment. But the exact height ofcentral rib 70, and other parts of the skid plate 10, will vary with thedesired stiffness and length of the skid plate.

The front end 12 has a generally flat end perpendicular to the concretesurface 22 and perpendicular to the slot 18 in the skid plate. Otherthan those differences, th front end 12, and the other parts of the skidplate 10, are as described in the previous embodiment.

The slot 18 is within about ⅛ of an inch of the sides of the cuttingblade 20, preferably along the entire length of the blade,advantageously along a majority of the length of the blade, andminimally along the sides of the cutting segments where the blade leavesthe concrete surface. Closer spacing between the sides of the slot 18and the adjacent sides of the cutting blade and the cutting segments onthe cutting blade are preferred, including spacings of 1/16 inch andless. The close spacing reduces raveling that occurs when the concretesurface 22 is cut before the surface has reached its typical rock-likehardness. What constitutes acceptable raveling can vary, but as usedherein acceptable raveling is that which is less than would occur with adown-cut, water lubricated saw cutting the next day on the same concretesurface.

The leading end of the slot 18 is preferably about ¼ of an inch from thecutting segments but the blade 20 moves relative to the concrete surface22 during cutting, so the distance between the leading end of the skidplate and the cutting blade will vary. Details are found in U.S. Pat.No. 4,769,201, the complete contents of which are incorporated herein byreference.

The slot 18 is preferably cast into the skid plate 10. But depending onthe material used to make the middle portion 16 the slot could be cut bythe blade 20. Indeed, the skid plate could be cast without slot 18 andthe user could plunge the cutting blade through the middle portion 16 toform the slot 18. This is possible because the concrete cutting blades20 are so durable, but using the cutting blade to form the slot 18 isundesirable if the skid plate is a ferrous based alloy because of theresulting wear on the cutting blade in forming the cut. If the skidplate is of a material other than steel or an iron based alloy then itis more practical to have the user form the slot 18 by plunging theblade 20 through the middle portion 16. Alternatively, a post castingstep of manufacturing could include mounting the cast skid plate on afixture and cutting the groove 18 in a middle portion 16 that was castwithout the slot, by plunging a cutting blade through the skid plate toform the slot. This slot formation could be performed by the user, butis less desirable if the skid plate 10 is formed of a ferrous basedmaterial because it will cause wear on the concrete cutting blade.

The skid plate 10 is shown with two mounting yokes 30, 34 and extendingalong the entire length of the blade 20. A skid plate made of stampedsteel strip had been previously used which mounted only at the front ofthe saw and extended about half the length of the cutting blade 20. Thatconfiguration did not work nearly as well as the skid plate with twomounting portions. A cast skid plate 10 having only one mount 30, or 34is nevertheless, believed suitable for use, but less preferable. A castskid plate with only one mounting portion is believed to have advantagesin performance, accuracy of manufacture, ease of manufacturing and costabove and beyond those of the prior art bent-metal skid plates.

Further, referring to FIG. 12, it is believed possible to use a skidplate 18 cast of two parts, a front and rear segment 98, 100,respectively, each segment having only one mounting yoke 30, 34 and eachsegment extending for less than the full length of the cutting blade 20measured along the concrete surface 22. Only the front segment 98 couldbe used, but is less desirable than using both segments 98 and 100. Therear segment 100 would be used by itself only if the blade 20 exited theconcrete within the slot contained in the rear segment 100 and then onlyit was the leading end which initially cut the groove in the concrete.Preferably the front skid plate segment extends from about ¼ to ½ thelength of the blade 20 measured at the concrete surface 22. But therelative proportions of each segment 98, 100 of the two-piece skid plate10 can vary. Preferably each skid plate segment 98, 100 has a leadingend inclined away from the concrete in order to avoid digging into theconcrete surface 22, and a trailing end that is also inclined away fromthe concrete. Inclined surfaces that are curved are preferred. A leadingend that is also angled relative to the direction of travel, like angles60, 62, are also preferred on each segment 98, 100. Because the slot 18adjacent the up-cutting edge of the blade 20 wears fastest, thispartial-length skid plate offers the possibility of physically replacingan entire portion of the skid plate 10 which is worn and reusing theportion which is not completely unsuitable for use.

The skid plate portions 98, 100 can be fastened to the saw by passingtwo pins or threaded fasteners 102 through the mounting portions 30, 34into a mating portion of the saw. For the front portion 98, the frontmounting portion can be modified to form a vertical flange which isbolted to the saw with two bolts. The same mounting could be used on therear portion 100. Alternatively, a bracket could be placed on front andrear pistons 32, 36 to allow two pins or fasteners to fasten to themovable pistons, as shown on the rear portion 100. The prior artincludes a partial skid plate made of bent, slotted sheet metal that wasbolted to the front of a saw using two bolts. The cast skid plate parts98, 100 are believed to be more accurately formed to the desired shapethan these prior art bent strips of metal.

Referring to FIGS. 13-14, a further embodiment is shown which uses asingle connection to the saw. The skid plate 10 has only the frontsegment 98 with the front 12 having the angled surfaces 60, 62, but withthe middle portion 16 ending rather than being connected to end 14. Theslot 18 extends through the middle portion 16, with a tunnel 23 formedin the lower surface 24. This embodiment of the skid plate 10 has asingle connection to the saw, through the front mounting shaft or piston32 in cooperation with the front yoke 30, each of which are modifiedfrom the prior embodiments.

The front yoke 30 has a left and right yoke 30L, 30R each of which hasan aligned hole 104 therthrough through which a shaft of a snap pin 106removably extends. The snap pin 106 has a spring lock 108 which ispermanently fastened to one end of the snap pin and releasably fastenedto the opposing end of the snap pin to releasably lock the snap pin 106to the skid plate and saw during use, as described later.

Between the left and right yokes 30L, 30R the front portion 12 has arecess into which the distal end of the front piston 32 fits. In thisrecess a resilient member 110 is placed. The resilient member 110 isshown as a bent leaf spring having a first end fastened to the frontmount 12 and having the opposing, second end bent generally into aC-shape relative to the first end. The second end preferably extends atan angle of about 45° relative to the horizontal. A flat strip of metalis believed suitable for the resilient member 110, but other types ofsprings and resilient members could be used, including coil springs,torsion springs, resilient elastomeric materials or rubber.

The distal end of the front mounting portion, shown as piston shaft 32,has a hole 112 sized and aligned to receive the shaft of the snap pin106 passing through the front mounting yokes 30. The distal end of thefront mount 32 abuts the resilient member 110 causing the skid plate 10to rotate toward the concrete surface 22 during cutting. The resilientmember 110 helps maintain the bottom surface 24 of the skid plateagainst the concrete during cutting in order to reduce or preventraveling.

To limit the rotation of the skid plate 10 relative to the saw, aportion of the skid plate abuts a portion of the saw. This can beachieved various ways, including fastening a flexible member to both thesaw and skid plate to limit the relative rotation of the skid plateabout pin 106. But preferably a portion of the skid plate 10 abuts thefront mount 32, or vice versa. Advantageously, but optionally, thedistal end of shaft 32 has an outwardly extending protrusion 114, whichcan take various forms such as a boss, a post, a flange, etc, but whichpreferably comprises ridge 114 located to engage the distal or top endof mounting yokes 30 or some other projection extending from the skidplate 10. The ridge 114 is shown as formed by flats 116 on thecylindrically shaped distal end of the front piston 32, which leave aportion of the cylindrical piston 32 extending outward from the flats toform a ridge 114 on each opposing side of the front piston 32. Theridges 114 are located relative to the top of the yokes 30 so that asthe skid plate 10 pivots about the shaft of snap pin 106, the ridges 114will hit the tops of the yokes 30 to limit the rotation.

Alternatively, the recess in the front end 12 which is located betweenthe yokes 30L and 30R could have a front ridge sized to hit the distalend of the shaft 32 to limit the rotation of the skid plate 10 aboutshaft 30, or a post or protrusion on the end of the shaft 32 could hit aportion of the front end 12 to limit motion of the skid plate. Likewise,referring to FIG. 15, a protrusion 114 on opposing sides of the shaft 32could abut shaped ends of the yokes 30L and 30R to limit rotation.Various other ways to limit the rotation will be apparent to one skilledin the art given the present disclosure.

In use, the distal end of front mount 32 presses against the resilientmember or spring 110 urges causing the spring to urge the skid plate 10toward and against the concrete while the blade 20 extends through theslot 18 to cut the concrete surface. The spring is selected to providesufficient force to maintain the skid plate against the concrete duringcutting so as to reduce, and preferably to prevent raveling. Therestraint system, such as the motion limit formed when ridge 114 hitsthe top of the mounting yokes 30, restrains movement of the skid plateso that when the blade and skid plate are withdrawn out of the concrete,the lower end of the skid plate does not drag on the concrete surface 22so as to mark that surface. The snapper pin 106 allows for removal andreplacement of the skid plate 10. The snapper pin 106 and its releasablespring lock 108 could take various forms, including pins with springloaded detents.

The skid plate 10 preferably extends at least past the cutting segmentsof the up-cutting portion of the cutting blade, and can extend for anylength of the blade. Preferably the skid plate 10 extends for the entirelength of the blade 20 measured along the concrete surface 22 (FIG. 1).The skid plate 10 is shown mounted to the leading end of the saw throughthe front mount 32, and then extending rearward. But it could be revisedfor mounting at the trailing end to rear mount 36, and extend forward.Whichever orientation is used, the leading end is preferably rounded orinclined in order to avoid digging into the concrete surface 22.

Referring to FIGS. 16-17, a further embodiment is shown in which a plate120 is releasably fastened to the cast skid plate 10. The plate 120comprises a sheet of material having a flat lower surface to smoothlyabut the concrete surface 22 (FIG. 1) during cutting. The plate 120 canhave various shapes, but preferably is shaped to conform to the bottomsurface 24 (FIG. 4) of the skid plate 10, and the shape of the bottomcan vary. The depicted plate 120 preferably, but optionally has twoinclined leading ends 60 a, 62 a, and a slot 18 a. The slot 18 a isshown ending in the plate 120. The slot can be preformed in the plate120, or it can be cut by the cutting blade 20 (FIG. 8) after the plateis fastened to the skid plate 10. The plate has an upward-extendingflange 122 along at least a portion of one side of the skid plate 10,with mounting tabs 124 at opposing ends. Preferably, but optionally, thetabs which are located to correspond with fasteners 126 extending fromthe skid plate 10. The front and rear portions 12, 14 are sufficientlythick that a threaded hole can be formed to accommodate a threadedfastener 126, and thus the tabs 124 preferably align with holes andfasteners 126 placed in the front and rear portions 12, 14. Thefasteners 126 extend through holes in the tabs 124, with threaded knobs128 fastening the tabs 124 and plate 120 to the skid plate 10. The plate120 can be cast of metal or other material, or extruded from a polymermaterial, or punched and formed from strip metal such as steel oraluminum.

In use, the plate 120 is releasably fastened to the skid plate 10 bymanually fastening the knobs 128 and fasteners 126 to the plate 120 andskid plate 10. The skid plate 10 provides support for the plate toprevent it from deforming and allowing raveling. The fasteners 126 andknobs 128 should cooperate with the tabs 124 sufficiently to hold theplate 120 flat against the bottom 24 of skid plate 10. If the plate 120is angled relative to the skid plate 20 the cutting blade 20 may cut andwiden the slot 18 a, and that could increase raveling of the concretesurface 22 during cutting.

The plate 120 can be used to reduce wear of the skid plate 10, or it canbe used after the slot 18 in skid plate 10 has become too wide toprevent raveling of the concrete during cutting. The flange 122 helpsalign and stiffen the plate 120, but could be omitted if desired. Aflange on the opposing side of the plate 120 could be provided ifdesired, as could additional fasteners 126 and knobs 128. Further, oneor both of the fasteners 126 could comprise pins and a different type ofreleasable lock could be used instead of the knob 128 (e.g., cotterkeys, snap rings, etc.). If the slot 18 a is preformed in the plate 120,it is preferably aligned and located to coincide with the slot 18 inskid plate 10, when mounted to the skid plate 10. The fasteners 126preferably fasten to the ends 12, 14, but could fasten to the side ribs72 and/or 74, or to one or more of the shields 76. As the skid plate 10is cast rather than formed of strip metal, suitably strengthened bossescan be readily located to accommodate various types of fasteners 126.

Referring to FIGS. 16 and 18, the slot 18, 18 a preferably extends tothe trailing end of the skid plate 10 and the plate 120 in order toavoid having the plate 120 trowel over the cut groove. The slot 120could be formed to extend until it opens onto the trailing end of theplate 120. Alternatively, as shown in FIG. 18, a shorter, and preferablywider rear slot 130 could be formed in the plate 120 and extend from thetrailing end forward. If so, the plate 120 is preferably made without apre-formed slot 18 a. When the slot 18 a is cut by a user plunging theblade 20 (FIG. 1) through the plate 120, the cut slot 18 a joins therear slot 130 to prevent troweling of the concrete. Having the blade 20form the slot 18 a in plate 20 reduces the required accuracy with whichthe plate 120 is aligned with the skid plate 10, as the slot 18 a ispreferably close to the cutting segments of the blade 20 during use.This rearwardly located slot 130 is usable with the various embodimentsdiscussed herein.

Referring to FIGS. 19-21, a further embodiment is shown in which theplate 20 is as generally described above, but in which the fastener 126takes the form of a pin with a spring loaded detent, as shown in FIG.20. In this embodiment the fastener 126 has one end threaded to engagemating threads on the skid plate 10. The opposing end of the fastenerhas a spring loaded detent 132 adjacent a distal end that is tapered tobetter fit through mating holes in the tabs 124. The detent 132 extendsthrough the mounting tab 124 and expands to prevent removal of the tabuntil the detent 132 is depressed. The spring loaded detents 132 areknown in the art and not described in detail. But the detents 132 allowquick removal and replacement of the plate 120, while the pins 126 arebelieved suitable to provide the alignment of the plate 120 with theskid plate 10.

Referring to FIGS. 22-23, a further embodiment is shown for removablyfastening a version of plate 120 to the skid plate. The plate 120 has aflange 122 along each opposing longitudinal side of the plate with theflanges spaced far enough apart that a skid plate 10 can fit betweenthem. Preferably there is a snug fit between the skid plate and theflanges 122 to restrain movement of the plate 120. The opposing flangeshave a plurality of tab 124 on each flange. The tabs 124 on one flange122 are aligned with the tabs on the opposing flange, so that a threadedfastener 126 can pass through aligned holes in the opposing tabs. Thefastener 126 preferably has an enlarged head on one end, and threadsengaging a nut on the opposing end. The tabs 124 are located adjacentthe ends 12, 14 so that when the fastener passes through the holes inthe tabs, the fasteners abut the front and rear ends 12, 14 to keep theplate 120 from substantial movement along the longitudinal axis 64. Therear fastener 126 pushes against the rear end 14 to push the plate 120when the saw moves forward during cutting. The front fastener 126 pushesagainst the front end 12 when the saw is pulled backwards, in order tomove the plate 120. Preferably the fasteners 126 are located relative tothe skid plate 10 so that the plate 120 is snugly held against the skidplate to help prevent movement of the plate 120 relative to the skidplate 10.

The fasteners 126 cooperate with the plate 120 to encircle narrowerportions of the skid plate 10 and hold the plate 120 so it moves withthe skid plate to maintain sufficient alignment of the slots 18, 18 a tosupport the concrete adjacent the cutting blade 20 and reduce or preventraveling. The plate 120 preferably, but optionally, has a shape thatmatches the shape of the bottom 224 of the skid plate 10, and this isshown with inclined front ends 60 a, 62 a. Instead of threaded fasteners126, detent pins, pins with spring clip fasteners, or other removable,elongated fasteners could be used. Further, the tabs could extend fromthe bottom plate 120 rather than forming a portion of the side flanges122.

Further, the tabs 122 could be omitted and the two fasteners 126 couldpass through a hole on the skid plate. For example, a boss could beformed on the upper surface of the skid plate with a hole in the bossthrough which one of the fasteners 126 extends. Two such bosses to holda forward and rearward fastener 126 are believed sufficient.

To attach the plate 120, it is pressed against the bottom 24 of the skidplate 10 so the holes in the tabs 124 project above the side ribs 72,74. The fasteners 126 are passed through a pair of aligned, opposingholes in the tabs 124 so they abut opposing ends 12, 14. To remove andreplace the plate 120, the process is reversed. Some vertical movementbetween the plate 120 and skid plate 10 is permissible in the plane ofthe cutting blade 20, but any such movement is preferably kept small toenhance the protection against raveling.

Referring to FIGS. 24-25, a clip-on plate 120 is shown having at leastone clip 136 on each opposing side of the plate 120. The clip 136preferably comprises a portion of the plate 120 which is bent upwardsand inwards to form a resilient member of sufficient length that adistal end of the clip can extend over a mating edge of the skid plate10. The clips 136 are preferably located to extend over the side ribs72, 74 adjacent the juncture of the side ribs with the ends 12, 14 sothe clips 136 abut the ends 12, 14 to restrain longitudinal movement ofthe plate 120 relative to the skid plate 10. Engagement of the side ribs72, 74 by the clips 136 restrains lateral movement of the plate 120relative to the skid plate 10. Preferably the distal end of each clip136 has an outwardly extending portion 138, such as a finger tab,sufficiently sized to allow a person's finger to engage the portion 138and bend the clip 136 sufficiently to allow the engagement anddisengagement of the clips 136 with the side ribs 72, 74. The clips 136resiliently engage the skid plate 10 to allow easy attachment anddetachment of the plate 120 on the skid plate. If desired, notches couldbe formed on the side ribs 72, 74, or other portions of the skid plate10, specifically configured to engage the clips 136. Four clips 136 areshown, but the number, size and location can vary.

In this embodiment the plate 120 is shown with a square leading endrather than an inclined end. The particular shape will vary. Preferablythe leading end is curved or inclined away from the concrete surface 22(FIG. 1) to prevent marking the surface, or alternatively the plate 120is made of material which will cause the leading end to soon take acurved or rounded shape.

To attach the plate 120, it is positioned along the bottom 24 of theskid plate 10 and the tabs 136 along one side are engaged with one ofthe side ribs 72, 74. The plate 120 is then rotated so the other clips136 engage the opposing side rib 72, 74, with the clips 136 bending toallow the engagement. To disengage the plate 120, the finger tab 138 isused to bend the clip 136 away from the skid plate 10 and allow removalof the plate 120.

Referring to FIGS. 26-27, a further embodiment is shown in which theplate 120 has flanges 122 extending a substantial length of the plate120, and preferably along the entire length. More than half is asubstantial length. The flanges 122 have a distal end which is shaped toextend laterally over the side ribs 72, 74 to engage the ribs and holdthe plate 120 to the skid plate. Preferably, but optionally, the distalends of the flanges 122 have a C-shape to hook over the ribs 72, 74 andextend back toward the bottom of the plate 10. The side flanges 122 formresilient members which urge the distal ends of the flanges 122 intoreleasable engagement with the side ribs 72, 74. The flanges 122preferably extend between the ends 12, 14 so that the distal ends of theflanges 122 abut the ends 12, 14 to limit longitudinal motion of theplate 120 relative to the skid plate 10. The flanges 122 are spacedapart so they abut the ribs 72, 74 and thus also limit the lateralmovement of the plate 120 relative to the skid plate 10. The ribs 72,74, or ends 12, 14 could be specially configured to engage a portion ofthe flange 74 and limit longitudinal motion between the parts.

In use, one of the flanges 122 is placed so its distal end engages oneof the side ribs 72, 74, between the ends 12, 14. The plate 120 is thenrotated and pressed so that the flanges 122 bend to allow the distal endof the un-engaged flange 122 to engage the other side rib 72, 74. Theflanges 122 snap-lock the plate 120 to the skid plate. To remove theplate 120 from the skid plate 10, one or both of the flanges 122 arebent away from the side ribs 72, 74 and the plate is removed. Ifdesired, one or more outwardly extending finger engaging protrusions ortabs 138 (as described in FIGS. 24-24) could be placed on the flanges122 to make it easier to bend the flanges 122 and engage or disengagethe plate 120 from the skid plate 10.

Referring to FIGS. 28-29, a further embodiment is shown in which a plate120 is removably fastened to the bottom 24 of the skid plate 10 by afastener 140. The plate 120 is shaped to conform to the shape of thebottom 24. A plurality of holes is formed through the plate 120 andfasteners 140 extend through the holes to fasten the plate 120 to theskid plate 10. Two fasteners 140 are shown, at opposing ends of theplate 120 and at opposing ends of the skid plate 10. The fasteners 140are shown as screws, one engaging the front 12 and one engaging the rear14 of the skid plate.

In the depicted embodiment the plate 120 has a slot 18 a which endsinternally to the plate 120 so the trailing end of the plate 120 trowelsover the groove cut in the concrete surface, with one of the fasteners140 being on the longitudinal axis 64 in which the slot 18 a and blade20 (FIG. 1) are located. It is preferable that the fastener 140 belocated off the longitudinal axis 64 so that the groove 18 a could beextended to the distal end of plate 120, as by the use of a partial slot130 described in FIG. 18.

Referring to FIGS. 30-31, a further embodiment is shown in which anadhesive 143 is placed over at least a portion, and preferably over allof the upper surface of the plate 120. The adhesive 143 abuts the bottom24 of the skid plate 10 to hold the parts together. A removable backingpaper is preferably placed over the adhesive 140, to protect theadhesive during non-use. The backing paper is removed shortly before theplate 120 is fastened to the bottom of the skid plate. The plate 120 ispried off the skid plate 10 by using a screwdriver or putty knifeinserted between the plate 120 and bottom 24.

Referring to FIGS. 32-33, a further embodiment is shown in which plate120 has a resilient locking tab 142 extending therefrom to engage amating recess in the skid plate 10. Preferably, there are front and rearlocking tabs 142 a, 142 b, respectively. Further, the front locking tab142 a is preferably, but optionally, formed by upsetting material fromthe slot 18 a so the tab 142 a extends upward from the plate 120 andforms a resilient member with a distal end 144 shaped to hook over andengage a mating surface. The location and shape of the resilient lockingmember 142 and locking end 144 can vary to form a snap-lock releasablyholding the parts together. Ideally, the locking tab 142 a extendsthrough slot 18 and the distal end 144 engages the upper surface of theskid plate 10 adjacent the leading end of the slot 18, either on one ofthe sides of the slot or on the leading end of the slot. The resilientlocking tab 142 a can be viewed as a resilient prong that engages theedges around a hole or slot through which the tab 142 a extends in orderto form a releasable snap-lock. Various configurations of such resilientsnap-locks can be devised using the disclosure herein, including snaplocks that extend through circular holes through the skid plate ratherthan extending through the slot 18.

The trailing locking tab 142 b could have the same construction as thefront locking tab 142 a, but preferably the rear locking tab is aprotrusion formed from upsetting material from the slot 18 a into ashape that fits in the slot 18 and engages the trailing end of the slot18. The front locking tab 142 a releasably holds the plate 120 to theskid plate 10, while the rear locking tab 142 b prevents the plate 120from moving rearward along longitudinal axis 64. Both locking tabs 142a, 142 b cooperate to prevent lateral movement of the plate 120 relativeto the skid plate 10.

In use, the plate 120 is aligned with the skid plate 10 and the rearlocking tab 142 b is placed into and abutting the rear of slot 18 in theskid plate 10. The front locking tab 142 a is then bent into the frontof the slot 18 and the plate 120 is rotated so the front tab 142 apasses through the slot 18 and the distal end 144 engages the uppersurface of the skid plate. For removal, the distal end 144 is manuallyengaged with a user's finger and bent toward the distal end 14, torelease the plate 120. Alternatively, the plate 120 could be manuallypulled away from the skid plate 10 and thus manually overcome theretention force of the locking tab(s) 142 by pulling on the plate 120.

The various embodiments of FIGS. 16-33 provide means for removablyfastening a plate 120 to the skid plate 10, through the use of variousfasteners 126, 140 and releasable mechanisms 136, 141, 142. The plate ispreferably, but optionally shaped to conform to the shape of the bottom24 of the skid plate, but the shape can vary. The leading end ispreferably curved or inclined away from the concrete surface 24 (FIG. 1)to prevent marking the surface. The edges of the plate 120 are oftensquare edges, but they could also be curved away from the concretesurface, and could form short flanges that engage any or all of thevarious sides, ends and edges defining the bottom surface 24 of the skidplate, to better position the plate 120 relative to the skid plate 10and to help reduce marking of the concrete surface during cutting.

The plate 120 can be injection molded of plastic, or bent into shapefrom sheet metal stock or coiled metal. Or the plate 120 could also becast of metal, or formed of composites, or powdered metal or sinteredmetal, as could skid plate 10. The slot 18 a can be formed in the plate120, or cut into the plate by the first user of the plate shortly beforecutting the concrete surface. The trailing slot 130 in plate 120 ispreferably used with these various embodiments, but can be omitted.

A further advantage of the skid plate is seen in FIGS. 4 and 6. Thepistons 32 are located on opposite ends of the cutting blade and extendtoward the concrete surface. During cutting these pistons 32 pushagainst opposing ends of the skid plate. The distal ends of thesepistons 32 are fastened to the skid plate at a location that isvertically offset from the plane of the concrete, in part because ofsize and space limitations. The mounting yokes 30, 34 are likewisevertically offset from the middle or support portion 16 of the skidplate. In the prior art these mounting portions overhung the middlesupport portion 16, and that caused bending of the middle portion 16. Inthe present skid plate, the front and rear ends of the skid plateadvantageously extend to the concrete surface below the pistons 32 sothe skid plate is interposed between the concrete surface and the mounts32 to the saw. Further, the front and rear ends 12, 14 of the skid platepreferably abut the concrete below the pistons 32, so the force from thepistons can pass directly through the front and rear ends 12, 14 andonto the concrete in order to greatly reduce, and preferably eliminatethe bending of the skid plate middle portion 16. The ends 12, 14 arepreferably configured to be large enough that the weight of the sawpushing on the ends does not mark the concrete.

By interposing the ends 12, 14 between the mounts to the saw and theconcrete, the forces tending to bend and bow the middle portion 16 ofthe skid plate are significantly reduced. That reduction in bowingallows the use of less curvature in the skid plate to offset the bowingthat occurs during use. By extending the ends 12, 14 in front or andbehind each piston 32 a sufficient distance (depending on the mountingconfiguration), it is believed possible to effectively eliminate thebowing of the skid plate and thus remove the need to curve the skidplate to counteract any bowing. The configuration used to mount the skidplate to the saw, such as yokes 30, 34 allows variation in the locationof the forces that tend to bend the skid plate.

But by making the front end 12 extend in front or behind the piston 32 adistance sufficient to effectively remove a bending moment on the skidplate, the ability to use a segmented or partial length skid plate isenhanced. Most of the wear on the skid plate occurs at the leading endof the skid plate where the leading end of the up-cutting saw bladeexits the concrete surface. A segmented skid plate having a frontportion that extends past that up-cutting edge of the cutting blade butnot the entire length of the blade can reduce raveling, and can allowreplacement of that front segment more often at a lower cost thanreplacing an entire, full length skid plate. A rear segment of the skidplate can support the concrete at the trailing end of the blade, andneed not be replaced as often as the front segment.

While it is simpler to have the skid plate connect to the distal ends ofpistons 32 and extend directly to the concrete surface directly belowthose distal ends, it is possible to cast the skid plate ends 12, 14 toform an inverted U shape that contacts the surface in front of andbehind the location of the distal ends 32. A solid end 12, 14 is desiredbelow the connections to the saw, such as yokes 30, 34, because itreduces the uncertainties of deformation of shaped parts.

Referring to FIG. 5, a further embodiment is shown which uses a sidemounting yoke 150 fastened to the skid plate 10. The side mounting yokeis shown with a flange extending toward the saw and fastened to themiddle portion 14 of the skid plate 10. As shown, the mounting yoke 150is braced to the front and rear portions 12, 14 of the skid plate. Theside mounting yoke 150 can be mechanically or chemically (e.g.,adhesives) fastened to at least one side of the skid plate 10, but ispreferably molded or cast integrally with the skid plate. The sidemounting yoke 150 preferably fastens to, and could form, one of the sideribs 72, 74 and extends away from the concrete surface 22 toward thesaw. A hole 152 extends through the mounting yoke 150 so that a pinnedconnection can be used similar to that described in FIGS. 13-14. Thedescription of that pinned connection is not repeated.

The use of a centrally located mounting yoke requires locating a movablepiston at the location of the mounting yoke, or extending a mountingsupport between front and rear pistons 32, 36 to connect to the sidemounting yoke 150. The side mounting yoke 150 is preferably locatedslightly forward of the center of gravity of the skid plate 10 so thatthe skid plate rotates about an axis through the hole 152, with the rearend 14 downward, when the skid plate is not in contact with the concretesurface. That helps prevent the front 12 from digging into the concretesurface as the skid plate is lowered toward the concrete surface 22.Further, it is undesirable to locate the mounting yoke 150 so the hole152 is in line with the rotational axis of the cutting blade 20 becauseof the drive shaft rotating that cutting blade and because of the accessneeded to fasten the blade to the drive shaft. Thus, the yoke 150 isoffset forward of the drive shaft rotating the blade 20, or is offsetforward of the rotational axis of the cutting blade 20.

The side mounting yoke 150 allows the weight of the saw to be supportedmore toward the middle of the skid plate 10, and that reduces bowing ofthe ends 12, 14 relative to the concrete surface 22.

A single side mounting yoke 150 could be used, or two side mountingyokes could be used, one on each opposing side rib 72, 74. If two sidemounting yokes 150 are used, the second one is preferably, butoptionally, a mirror image of the yoke 150 shown in FIG. 5. This allowsa single piston to be used if only one side mounting portion 150 isused. Alternatively, two pistons, one on each side of the cutting blade20 could be used, each pinned to a separate side mount 150 on opposingsides of the cutting blade. Locating the mounting yoke 150 to only oneside of the slot 18 can cause twisting of the skid plate 10 about thesingle side mount and fastening the saw to two side-mounts can causetwisting of the skid plate 10 about the slit 18. But the offset isrelatively small (.5-2 inches) and the skid plate is relatively stiffalong the axis needed to oppose that bending, in order to minimize theeffects of deformation from the side offset.

The ability to eliminate the prior art truss used to curve the skidplate offers further advantages to the concrete saw. The truss extendedgenerally parallel to the middle portion 16, but vertically offsettoward the saw and away from the concrete. The presence of the trusslimited the size of the flange which helps clamp or fasten the cuttingblade 20 to a rotating arbor. By eliminating the truss the flange can bemade larger and can extend closer to the middle portion 16 of the skidplate. This increased diameter support not only helps support thecutting segments of the blade 20 and make the blade more rigid, but itplaces a greater surface of the flange in contact with the metal core ofthe cutting blade and that increases conduction and helps keep thecutting blade cooler. A cooler cutting blade is useful because the metalcore (over which the abrasive cutting segments are formed) can overheatand soften, leading to premature failure of blade or excessive wear ofthe cutting segments. The elimination of the truss by using the castskid plate thus helps the blade 20 run cooler and presumably lastlonger, and it allows a stiffer support which typically means astraighter cut and less wobble of the blade 20. A concrete cutting bladewith a mounting flange closer to the periphery than previouslyachievable is thus believed possible. During use the mounting flangecomes close to hitting, but does not abut the skid plate, with thecloseness being determined by the depth of cut of the groove 25 formedin the concrete.

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the invention,including various ways of fastening the skid plate to the saw. Further,the various features of this invention can be used alone, or in varyingcombinations with each other and are not intended to be limited to thespecific combination described herein. Thus, the invention is not to belimited by the illustrated embodiments but is to be defined by thefollowing claims when read in the broadest reasonable manner to preservethe validity of the claims.

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 33. (canceled)34. A skid plate for a concrete cutting saw, the saw having a rotatingblade with sides and rotating about a rotational axis to cut a groove ina concrete surface during use of the saw, comprising: an elongatedsupport portion having a longitudinal slot therein sized to fit withinabout ⅛ inch or less of the sides of the concrete cutting blade duringuse of the skid plate, the elongated support being slightly bowed anamount selected to substantially counteract bowing of the skid platethat occurs when the elongated support is urged against the concretesurface during cutting of the concrete, the elongated support beingintegrally cast or forged or machined in the bowed configuration; atleast one saw mounting portion connected to the skid plate.
 35. The skidplate of claim 34, wherein the at least one saw mounting portion extendsin front of a front mount on the saw and extends a distance sufficientto abut the concrete surface directly below the location of the frontmount on the saw during cutting.
 36. The skid plate of claim 34, whereinthe skid plate has a leading end that is thicker than the elongatedportion in a direction parallel to the plane of the cutting blade. 37.The skid plate of claim 34, wherein the skid plate has a leading andtrailing end each of which is thicker than the elongated portion in adirection parallel to the plane of the cutting blade.
 38. The skid plateof claim 34, where the elongated portion is cast of metal.
 39. The skidplate of claim 34, where the elongated portion is cast of metal and abottom of the skid plate has a coating on it that is harder than thecast metal.
 40. The skid plate of claim 34, where the elongated portionhas a bottom that has a hard coating on it.
 41. The skid plate of claim34, where the elongated portion is cast of a metal the dominant portionof which is other than iron.
 42. The skid plate of claim 34, where theelongated portion is cast of a polymer.
 43. The skid plate of claim 34,wherein there are two mounting portions, one of which comprises a slotextending along an axis toward and away from the elongated supportportion and configured to receive a pin orientated generally parallel tothe rotational axis and the other of which comprises a slot that isgenerally parallel to the concrete surface during cutting.
 44. The skidplate of claim 34, wherein the skid plate has a leading and trailing endand two opposing sides extending between the ends, with the leading endof the skid plate inclined from one side to the other in the directionof the trailing end.
 45. The skid plate of claim 34, wherein the skidplate has a leading and trailing end and two opposing sides extendingbetween the ends, and further has a top and bottom surface, with theleading end of the skid plate inclined from the top toward the bottomand from the leading end toward the trailing end.
 46. The skid plate ofclaim 34, wherein the skid plate has a leading and trailing end and theleading end of the skid plate has a V shaped configuration in the planeof the elongated portion with the point of the V oriented away from atrailing end and toward the leading end.
 47. The skid plate of claim 34,further comprising a plate configured to releasably connect to the skidplate so the plate is interposed between a bottom of the skid plate andthe concrete during cutting, the plate having a smooth bottom forabutting the concrete surface during cutting.
 48. The skid plate ofclaim 34, further comprising a plate configured to releasably connect tothe skid plate so the plate is interposed between a bottom of the skidplate and the concrete during cutting, and a mechanism releasablyfastening the plate to the skid plate.
 49. The skid plate of claim 34,further comprising a metal insert in the support portion at a leadingend of the slot in the skid plate.
 50. A skid plate for a concretecutting saw, the saw having a rotating blade with sides and rotatingabout a rotational axis to cut a groove in a concrete surface during useof the saw, the skid plate having a leading and trailing end withopposing sides and a top and bottom surface, the bottom surface beingadjacent to or abutting the concrete during cutting; comprising: anelongated support portion having a longitudinal slot therein sized tofit within about ⅛ inch or less of the sides of the concrete cuttingblade during use of the skid plate; at least one saw mounting portionconnected to the skid plate; and the leading end of the skid platehaving at least a portion inclined from one side toward the other sidein a direction toward the trailing end of the skid plate.
 51. The skidplate of claim 50, wherein the elongated portion comprises a polymerwith a metal insert at the location of an up-cutting edge of the cuttingblade and extending to the surface abutting the concrete.
 52. The skidplate of claim 50, wherein the elongated portion comprises a polymercast over a metal portion.
 53. The skid plate of claim 50, furthercomprising a plate configured to releasably connect to the skid plate sothe plate is interposed between a bottom of the skid plate and theconcrete during cutting, the plate having a smooth bottom for abuttingthe concrete surface during cutting.
 54. The skid plate of claim 50,where the elongated portion includes a polymer cast over one of a metalinsert or a metal plate.
 55. A skid plate for a concrete cutting saw,the saw having a rotating blade with sides and rotating about arotational axis to cut a groove in a concrete surface during use of thesaw, comprising: an elongated support portion having a longitudinal slottherein sized to fit within about ⅛ inch or less of the sides of theconcrete cutting blade during use of the skid plate; and at least onesaw mounting portion connected to the skid plate at a leading end of theskid plate, the mounting portion having a side shield on each opposingside of the skid plate, the side shield extending above at least aportion of a top surface of the leading end of the skid plate.
 56. Theskid plate of claim 55, wherein the saw mounting portion extends infront of a front mount on the saw and extends a distance sufficient toabut the concrete surface directly below the location of the front mounton the saw during cutting.
 57. The skid plate of claim 55, wherein theleading end of the skid plate is thicker than the elongated portion in adirection parallel to the plane of the cutting blade.
 58. The skid plateof claim 55, wherein the skid plate has a leading and trailing end eachof which is thicker than the elongated portion in a direction parallelto the plane of the cutting blade.
 59. The skid plate of claim 55, wherethe elongated portion is cast of metal the dominant portion of which isnot iron.
 60. The skid plate of claim 55, wherein the elongated portioncomprises a polymer cast over one of a metal plate or insert.
 61. Theskid plate of claim 55, further comprising a plate configured toreleasably connect to the skid plate so the plate is interposed betweena bottom of the skid plate and the concrete during cutting, the platehaving a smooth bottom for abutting the concrete surface during cutting.62. A skid plate for use on a concrete cutting saw having a cuttingblade that rotates about a first axis and extends through a slot in theskid plate to cut a groove in a concrete surface along a second axisthat is orthogonal to the first axis, the skid plate having a releasableconnection for releasable mounting the skid plate to the saw, the skidplate comprising: a leading end inclined away from the concrete surfaceand an elongated support portion both integrally cast, forged or cutfrom metal or polymer, the support portion having an elongated slottherein, the slot sized relative to the cutting blade to support theconcrete surface during cutting so it does not produce unacceptableraveling of the cut groove during use of the skid plate, the supportportion having a bottom.
 63. The skid plate of claim 62, where theelongated portion includes a metal insert at the location of anup-cutting edge of the cutting blade.
 64. The skid plate of claim 62,where the elongated portion comprises a polymer with a metal insert atthe location of an up-cutting edge of the cutting blade.
 65. The skidplate of claim 62, where the elongated portion comprises a polymer witha metal insert at the location of an up-cutting edge of the cuttingblade and extending to the surface abutting the concrete.
 66. The skidplate of claim 62, where the elongated portion comprises a polymer castover a metal portion.
 67. The skid plate of claim 62, where theelongated portion includes a plate over the bottom of the elongatedportion.
 68. The skid plate of claim 62, where the elongated portionincludes a polymer cast over one of a metal insert or a metal plate. 69.The skid plate of claim 62, where the elongated portion is cast of ametal the dominant portion of which is other than iron.
 70. The skidplate of claim 62, where the elongated portion comprises a polymer. 71.The skid plate of claim 62, wherein the skid plate is configured to abutthe concrete below the location of the releasable connection to the sawduring use of the skid plate.
 72. A method for use with a concretecutting saw, the saw having a rotating blade with sides and rotatingabout a rotational axis to cut a groove in a concrete surface during useof the saw, comprising: providing a skid plate having an elongatedsupport portion having a longitudinal slot therein sized to fit withinabout ⅛ inch or less of the sides of the concrete cutting blade duringuse of the skid plate, the elongated support being slightly bowed anamount selected to substantially counteract bowing of the skid platethat occurs when the elongated support is urged against the concretesurface during cutting of the concrete; providing at least one sawmounting portion, wherein the elongated support and at least one sawmounting portion are integrally cast, forged or machined from a singlepiece of material; providing a plate configured to removably attach tothe skid plate so the plate is interposed between a bottom of theelongated portion and the concrete during cutting.
 73. The method ofclaim 72, further comprising forming the elongated portion out of metal.74. A method for use with a concrete cutting saw having a cutting bladethat rotates about a first axis and extends through a slot in a skidplate to cut a groove in a concrete surface along a second axis that isorthogonal to the first axis, the saw having front and rear mounts onopposing ends of the cutting blade to fasten to the skid plate, the skidplate comprising: providing two saw mounting portions on the skid platelocated to correspond to the front and rear saw mounts and an elongatedsupport portion, the two mounting portions and support portion beingintegrally formed by casting, forging or cutting; further providing anelongated in the support portion, the slot sized relative to the cuttingblade to support the concrete surface during cutting so it does notproduce unacceptable raveling of the cut groove during use of the skidplate; and providing a plate configured to removably attach to the skidplate so the plate is interposed between a bottom of the elongatedportion and the concrete during cutting.
 75. The method of claim 74,further comprising forming the elongated portion out of metal.
 76. Themethod of claim 74, further comprising forming the elongated portion atleast partially out of a polymer.
 77. The method of claim 74, furthercomprising forming the plate out of metal.
 78. The method of claim 74,further comprising forming the plate out of a polymer.
 79. A method foruse with a concrete cutting saw having a cutting blade that rotatesabout a first axis and extends through a slot in a skid plate to cut agroove in a concrete surface along a second axis that is orthogonal tothe first axis, the skid plate comprising: providing the skid plate withfirst means for mounting the skid plate to the concrete saw andproviding the skid plate with second means for supporting the concretesurface during cutting, the first and second means being integrallyformed; providing a plate configured to removably attach to the skidplate so the plate is interposed between a bottom of the elongatedportion and the concrete during cutting.
 80. The method of claim 79,further comprising forming the elongated portion out of metal.